The present invention relates to black iron-based composite particles, a process for producing the black iron-based composite particles, and a paint and a rubber or resin composition containing the black iron-based composite particles. More particularly, the present invention relates to black iron-based composite particles not only having an excellent dispersibility in a vehicle, or a rubber or resin composition on the basis of a small amount of the carbon black which are desorbed from the surface of the black iron-based composite particles and a high blackness substantially identical to a blackness of carbon black fine particles used solely, even when carbon black is contained therein only in a small amount, but also capable of providing a paint for providing a coating film having an excellent acid resistance or a resin composition having an excellent aging resistance; a process for producing the black iron-based composite particles; a paint containing the black iron-based composite particles, which is excellent in acid resistance; and a rubber or resin composition containing the black iron-based composite particles, which is excellent in aging resistance.
Carbon black fine particles or magnetite particles are well known in the art as typical black pigments, and have been hitherto widely used as colorants for paints, printing ink, cosmetics, rubber or resin compositions or the like.
Among these black pigments, the carbon black fine particles are most excellent in blackness, and a coating film and rubber or resin composition prepared by using the carbon black fine particles also have an excellent acid resistance or aging resistance. However, since the carbon black fine particles have an average particle size as fine as about 0.005 to 0.05 xcexcm, it has been difficult to disperse the particles in a vehicle, or a rubber or resin composition. Further, since the carbon black fine particles have a bulk density as high as about 0.1 g/cm3, it has been difficult to handle the particles, resulting in deteriorated workability. Furthermore, it is also known that the carbon black fine particles have problems concerning safety and hygiene, such as carcinogenosis.
That is, as the amount of the carbon black fine particles used is increased, the blackness tends to become higher. However, when a larger amount of the carbon black fine particles is used, it is more and more difficult to disperse the particles in a vehicle, or a rubber or resin composition, resulting in not only deteriorated workability but also unfavorably causing problems concerning safety and hygiene.
On the other hand, the magnetite particles have a more appropriate particle size than that of the carbon black fine particles, especially an average particle size of about 0.08 to 1.0 xcexcm and are, therefore, excellent in dispersibility in a vehicle, or a rubber or resin composition, resulting in a high handling property. Further, the magnetite particles can show a further advantage such as non-toxicity. However, the magnetite particles are still unsatisfactory in blackness, and the coating film and the rubber or resin composition prepared by using the magnetite particles are also unsatisfactory in acid resistance and aging resistance.
Further, the magnetite particles tend to be magnetically aggregated because of magnetic attracting property thereof. In consequence, in order to improve the dispersibility in a vehicle, or a rubber or resin composition, it is known to use, as non-magnetic black iron-based particles, manganese-containing hematite particles or manganese-containing iron oxide hydroxide particles. However, the blackness of these particles is inferior to that of the magnetite particles.
In recent years, it has been required to improve various properties of black particles as colorants. There has been a strong demand for such black particles capable of showing useful properties of the carbon black fine particles as well as those of black iron oxide particles such as magnetite particles and black manganese-containing hematite particles or black iron oxide hydroxide particles such as black manganese-containing goethite particles.
Especially, it has been strongly demand to provide such black particles capable of showing a high blackness substantially identical to a blackness of the carbon black fine particles used solely, even when the carbon black fine particles which are deteriorated in workability such as handing property and have problems concerning safety and hygiene, are contained therein only in a small amount; capable of providing a paint for providing a coating film having an excellent acid resistance or a resin composition having an excellent aging resistance; and further capable of exhibiting an excellent dispersibility in a vehicle, or a rubber or resin composition.
To satisfy these demands, it has been attempted to produce black composite particles composed of the carbon black fine particles and the magnetite particles, and having useful properties of both the particles. For example, there are known 1) a method comprising steps of adding a water dispersion containing carbon black fine particles to a water suspension containing magnetite particles precipitated from an aqueous solution and then mixing and stirring the resultant mixture, thereby causing the carbon black fine particles to be absorbed onto surfaces of the magnetite particles (Japanese Patent Publication (KOKOKU) No. 50-13300(1975)); 2) a method comprising a step of introducing an iron-containing waste sludge in which high-molecular weight organic materials such as molasses are dissolved, and a carbon black-containing hot gas into a spray reactor at a temperature of 450 to 850xc2x0 C., thereby producing magnetite particles from iron salts and simultaneously bonding the carbon black onto surfaces of the obtained magnetite particles using the molasses as a binding accelerator (Japanese Patent Application Laid-open (KOKAI) No. 49-48725(1974)); 3) a method comprising steps of suspending carbon black in an iron salt-containing aqueous solution and then adding alkali to the resultant suspension to co-precipitate carbon black and magnetite particles, thereby obtaining a co-precipitated product whose surfaces are coated with carbon black (Japanese Patent Publication (KOKOKU) No. 55-39580(1980)); 4) a method comprising steps of adhering carbon black or the like on the surfaces of fine plate-like particles and fixing the carbon black or the like thereon using an anionic or cationic surfactant, a nonionic surfactant and an organic functional silane compound (Japanese Patent Application Laid-open (KOKAI) Nos. 6-145556(1994) and 7-316458(1995)); or the like.
At present, it have been most demanded to provide black particles having useful properties of the carbon black fine particles as well as those of the black iron oxide particles or black iron oxide hydroxide particles. However, all of the above mentioned known methods have failed to provide black particles satisfying these useful properties. Specifically, in the case of the above-mentioned method 1), the desorption percentage of the carbon black still remains high as described in Comparative Examples hereinafter. As a result, when the carbon black-adsorbed magnetite particles are dispersed in vehicle or resin compositions, the carbon black fine particles are desorbed therefrom, i.e., it becomes difficult to uniformly disperse the black particles in vehicles and resin compositions, thereby failing to sufficiently improve the blackness of a paint and rubber or resin composition prepared therefrom.
In the case of the above-mentioned method 2), in order to obtain black particles having a high blackness substantially identical to a blackness of carbon black fine particles used solely, it is required to use the carbon black fine particles in an amount as large as about 280 parts by weight based on 100 parts by weight of the magnetite particles. In the case of the above-mentioned method 3), in order to obtain black particles having a high blackness substantially identical to a blackness of carbon black fine particles used solely, it is also required to use the carbon black fine particles in an amount as large as about 100 to 400 parts by weight based on 100 parts by weight of the magnetite particles. In addition, the carbon black fine particles tend to be desorbed from the surfaces of the co-precipitated product. Further, in the case of the above-mentioned method 4), the particles obtained by this method are not only deteriorated in blackness, but also show a high percentage of desorption of the carbon black fine particles therefrom. Besides, such particles obtained by the method 4) are not black particles.
As a result of the present inventors"" earnest studies, it has been found that by forming a coating layer composed of at least one organosilicon compound selected from the group consisting of (1) organosilane compounds obtained from alkoxysilane compounds, (2) polysiloxanes or modified polysiloxanes and (3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds, on the surface of specific black iron oxide particle or black iron oxide hydroxide particle, and forming a carbon black coat on the formed coating layer such that the amount of the carbon black is 1 to 30 parts by weight based on 100 parts by weight of the black iron oxide particles or black iron oxide hydroxide particles, the obtained black iron-based composite particles can have an excellent dispersibility in a vehicle, or a rubber or resin composition on the basis of a small amount of the carbon black which is desorbed from the surface of the black iron-based composite particles and a high blackness substantially identical to a blackness of carbon black fine particles used solely, even when the carbon black is contained therein only in a small amount, and can provide a coating film having an excellent acid resistance and a rubber or resin composition having an excellent aging resistance. The present invention has been attained on the basis of the above finding.
An object of the present invention is to provide black iron-based composite particles not only having a high blackness substantially identical to a blackness of carbon black fine particles used solely, even when carbon black is contained therein only in a small amount, but also capable of providing a paint for providing a coating film having an excellent acid resistance and a rubber or resin composition having an excellent aging resistance.
Another object of the present invention is to provide black iron-based composite particles showing a low percentage of desorption of carbon black therefrom, and an excellent dispersibility in a vehicle, or a rubber or resin composition on the basis of a small amount of the carbon black which are desorbed from the surface of the black iron-based composite particles.
A further object of the present invention is to provide a process for producing black iron-based composite particles not only having an excellent dispersibility in a vehicle, or a rubber or resin composition and showing a high blackness substantially identical to a blackness of carbon black fine particles used solely, even when carbon black is contained therein only in a small amount, but also capable of providing a paint for providing a coating film having an excellent acid resistance and a rubber of resin composition having an excellent aging resistance.
A still further object of the present invention is to provide a paint showing less change in gloss and lightness according to an acid resistance test for coating films.
A still further object of the present invention is to provide a rubber or resin composition which exhibits a small deterioration of the rubber or resin used therein.
To accomplish the aims, in a first aspect of the present invention, there is provided black iron-based composite particles comprising:
as a core particle black iron oxide particle or black iron oxide hydroxide particle having an average particle size of 0.08 to 1.0 xcexcm;
a coating layer formed on the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one organosilicon compound selected from the group consisting of:
(1) organosilane compounds obtained from alkoxysilane compounds,
(2) polysiloxanes, or modified polysiloxanes and
(3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds; and
a carbon black coat formed on the said coating layer comprising said organosilicon compound, in an amount of 1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles.
In a second aspect of the present invention, there is provided black iron-based composite particles comprising:
black iron oxide particles or black iron oxide hydroxide particles having an average particle size of 0.08 to 1.0 xcexcm;
a coat formed on at least a part of the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one compound selected from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon;
a coating layer formed on the coat formed on the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one organosilicon compound selected from the group consisting of:
(1) organosilane compounds obtained from alkoxysilane compounds,
(2) polysiloxanes, or modified polysiloxanes and
(3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds; and
a carbon black coat formed on the said coating layer the comprising said organosilicon compound, in an amount of 1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles.
In a third aspect of the present invention, there is provided a process for producing black iron-based composite particles, which process comprises:
mixing as core particles black iron oxide particles or black iron oxide hydroxide particles having an average particle size of 0.08 to 1.0 xcexcm together with at least one compound selected from the group consisting of:
(1) alkoxysilane compounds,
(2) polysiloxanes or modified polysiloxanes, and
(3) fluoroalkylsilane compounds by using an apparatus capable of applying a shear force to the core particles, thereby coating the surface of said black iron oxide particle or black iron oxide hydroxide particle with the said compounds;
mixing the black iron oxide particles or black iron oxide hydroxide particles coated with the said compounds with carbon black fine particles having an average particle size of 0.005 to 0.05 xcexcm in an amount of 1 to 30 parts by weight based on 100 parts by weight of the core particles by using an apparatus capable of applying a shear force, thereby forming a carbon black coat on the coating layer comprising the organosilicon compounds.
In a fourth aspect of the present invention, there is provided a paint comprising:
a paint base material, and
black iron-based composite particles comprising:
as a core particle black iron oxide particle or black iron oxide hydroxide particle having an average particle size of 0.08 to 1.0 xcexcm;
a coating layer formed on the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one organosilicon compound selected from the group consisting of:
(1) organosilane compounds obtained from alkoxysilane compounds,
(2) polysiloxanes, or modified polysiloxanes and
(3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds; and
a carbon black coat formed on the said coating layer comprising said organosilicon compound, in an amount of 1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles.
In a fifth aspect of the present invention, there is provided a rubber or resin composition comprising:
a base material for rubber or resin composition, and black iron-based composite particles comprising:
as a core particle black iron oxide particle or black iron oxide hydroxide particle having an average particle size of 0.08 to 1.0 xcexcm;
a coating layer formed on the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one organosilicon compound selected from the group consisting of:
(1) organosilane compounds obtained from alkoxysilane compounds,
(2) polysiloxanes, or modified polysiloxanes and
(3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds; and
a carbon black coat formed on the said coating layer comprising said organosilicon compound, in an amount of 1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles.